Residual Current Devices (RCDs) / Residual Current Circuit Breakers with Overcurrent Protection (RCBOs)
Residual Current Devices (RCDs) and Residual Current Circuit Breakers with Overcurrent Protection (RCBOs) are electrical devices for protection against electrocution or fire risk caused by an earth fault. This section provides basic guidance on selection and installation of RCDs / RCBOs with Powerwall systems when mandated by local code.
RCDs / RCBOs on Site-Level Circuits
Site-level RCDs / RCBOs may be required on TT earthing networks to ensure disconnect time per regulation or to protect cabling on site. It is well known that switching Neutral and Line conductors may occasionally cause nuisance tripping on upstream RCDs / RCBOs. One of the following two methods must be used to avoid risk of site-level RCD / RCBO nuisance tripping:
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Option 1: Relocate
site-level RCD / RCBO into the Backup Gateway enclosure after Gateway’s
contactor (see figure below)
- If the Backup Gateway is installed near the service entrance and DNO meter, relocate the site RCD / RCBO after the internal contactor by connecting to the ‘Home’ terminals.
- In this configuration, all downstream home wiring remains protected by the site-level RCD / RCBO.
- Incoming mains cables must be double-insulated.
Figure 1. Relocating Site-Level RCD / RCBO into Backup Gateway after the Contactor 
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Option 2: Use Type-S
time-delayed RCD / RCBO upstream of Backup Gateway
- Type-S RCD / RCBOs are used for site-level protection to provide selectivity by introducing a time delay, ensuring any downstream RCDs / RCBOs trip first.
- The delay provided by a Type-S RCD / RCBO is an effective mitigation of nuisance tripping.
Figure 2. Using Type S Time-delayed RCD / RCBO Upstream of Backup Gateway 
RCDs / RCBOs on Circuits Supplying Powerwall
Where required by local regulations, the installer may select an RCD or RCBO with an appropriate residual current rating for the circuit supply of Powerwall 3. However, to minimize the risk of nuisance trips, a 300 mA Type AC or A RCD / RCBO is recommended.
Powerwall 3 does not require a Type B RCD / RCBO, as it is not capable of feeding DC fault current into the electrical installation as per IEC 60364-7-712:2002.
